I very un-mathematically tried to get the perfect amount on my card so that it would come out to $0.00 when it was last swiped, but the best I could do without a paper, pen and/or calculator was down to $0.25 left on my card which isn’t bad. Problem is also that I have two Metrocards with cash on them right now so I’d love to get all the money out of one so I wouldn’t feel like I was wasting those small amounts when I threw the card away.

EDIT: My friend Fo just sent this link to me, thanks! http://www.nycmetrocardcalculator.com/